College of Agriculture, Engineering
and Science (CAES)

Tackling Rice Yellow Mottle Virus in Tanzania

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A burning desire to improve the lot of small-scale farmers like his parents inspired Dr William Suvi to pursue a career in plant breeding.

Suvi hails from Mngeta village in Kilombero district in the Morogoro region in Tanzania.

‘My family were peasants cultivating rice, maize and other crops like sweet potato and vegetables,’ he said. ‘I was motivated to study plant breeding in order to improve yields for farmers. In my village, most farmers including my parents use landraces that produce low yields, and there is not enough for food and to sell as surplus. Because of this, farmers are unable to pay for basic items like clothes, school fees and health services.’

Suvi’s tertiary education includes a BSc in general agriculture and an MSc in crop science, specialising in agriculture and plant breeding, respectively, at Sokoine University of Agriculture in Tanzania.

‘I selected my topic based on the research gap affecting farmers in rice production,’ he said. ‘The title was: Breeding for Resistance to Rice Yellow Mottle Virus and Improved Yield in Rice in Tanzania.’

Despite the fact that rice production and consumption have increased steadily in sub-Saharan Africa (SSA), rice is the largest imported commodity crop in the region, due to domestic farmers’ low productivity.

Suvi’s thesis notes that this is due to a number of biotic and abiotic stresses and socio-economic constraints, with rice yellow mottle virus (RYMV) the most important biotic challenge in SSA, causing yield losses ranging from 20% to 100%.

According to Suvi, ‘current RYMV disease management through generic crop protection chemicals is not economically viable, nor is it successful due to the large number of vector species disseminating the virus. In addition, cultural practices are ineffective against RYMV because the virus is spread by several agents, including insect vectors.’

He said the use of RYMV-resistant cultivars remains the most effective, economically viable and environmentally friendly method for resource-poor farmers, but these resistant varieties have not yet been developed and deployed in SSA.

The first step in his research, which began in 2018, was to conduct a participatory rural appraisal (PRA) in order to assess farmer’s preferences, production constraints, and choice of rice varieties.

‘I then screened rice germplasm based on agronomic traits and resistance to RYMV under field hotspot conditions, and after that I assessed the genetic diversity and population structure of a selected population of rice genotypes,’ he said.

‘Finally population development and evaluation was done to determine the combining ability and gene action for RYMV disease resistance and agronomic improvement.’

The challenges faced in the course of his field work included a scarcity of rain and limited access to technology, such as a rice emasculator, to do crossing work.

Suvi, whose studies were funded by the Alliance for a Green Revolution in Africa, is currently working on cotton and rice breeding programmes in Tanzania.

Words: Shelagh McLoughlin

Photograph: Supplied